"Today the ZFS on Linux project reached an important milestone with the official 0.6.1 release! Over two years of use by real users has convinced us ZoL is ready for wide scale deployment on everything from desktops to super computers."

If the FAQ entry on their site is correct, I see no reason to involve lawyers:

"The combination of them causes problems because it prevents using pieces of code exclusively available under one license with pieces of code exclusively available under the other in the same binary. In the case of the kernel, this prevents us from distributing ZFS as part of the kernel binary. However, there is nothing in either license that prevents distributing it in the form of a binary module or in the form of source code."